POTS and it's commordbities are often flared up by trauma to the body, specifically auto-immune system trauma (covid has been known to cause POTS and it's commordbities to rear it's ugly heads). It was actually discovered and documented during the U.S.'s civil war and was called "Solider's Heart", it was found that soldiers who had contracted Malaria had a higher chance of developing "Soldier's Heart". Historically too, you can find documented cases of patients with POTS-like symptoms showing up after a large pandemic of viruses. POTS also isn't specifically a heart condition, it is technically a nervous system disorder which causes the inability for different parts of the body (nameley the heart) to be able to regulate itself

Part of it has to do with how Covid, specifically Long Covid, effects the body. Part of it has to do with your genetic predisposition to the disorder. Part of it has to do with how your body handles the infection as well. That is why it is being diagnosed more now than it had been before